Vacuum switch contacts

ABSTRACT

Improved vacuum switch contact members have been fabricated from an electrically conductive hard metallic matrix containing a dispersoid of an electrically conductive metallic material which is insoluble in the matrix and which has a relatively high vapor pressure when heated by an arc developed between two such contact members. A specific example of a 96 weight per cent nickel, two per cent beryllium and 2 per cent bismuth composition is disclosed.

States Ptent Waiter et al.

[ Apr. 11, 1972 [54] VACUUM SWITCH CONTACTS [72] Inventors: John L.Walter, Scotia; Harvey E. Cline, Schenectady; James D. Cobine, Rexford,

all of NY.

[73] Assignee: General Electric Company [22] Filed: Jan. 7, 1970 [2]]Appl. No.: 1,313

52 U.S.Cl ,.75/170,75/l76,200/l66 58 Field of Search ..75/170, 171, 176;148/32, 325;

[56] References Cited UNITED STATES PATENTS 3,437,479 4/1969 Nakajima..75/1 70 Primary ExaminerRichard 0. Dean Att0rneyRichard R. Brainard,Paul A. Frank, Charles T. Watts, Frank L. Neuhauser, Oscar B. Waddelland Joseph B. Forman ABSTRACT 2 Claims, No Drawings VACUUM SWITCHCONTACTS This invention relates to electrical contacts for use in vacuumswitches.

As implied by the name, a vacuum switch is a device for selectivelyinterrupting an electrical current by physically separating a pair ofelectrical contact members in a vacuum environment and, of course,alternatively by physically moving one or both of a pair of such membersinto physical, electrically conducting, contact with each other.Depending upon the characteristics of the contact members, certainadverse affects may be produced in the circuitry associated with theoperation of the switch, particularly upon the interruption of currentflow, such as the resulting undesirable current surge produced bychopping or a too sudden interruption of the current flow. A highbreakdown and recovery strength is also desirable in such switches. Itwould be desirable to provide vacuum switch contact members which haveimproved properties or characteristics over the alloy members presentlyused and such is a principal object of this invention.

Briefly stated, and in accordance with one aspect of the invention, itwas conceived that electrical contact members for such switches shouldbe reasonably good electrical conductors, be physically hard, i.e.resist plastic deformation, have a high are stability upon brakingcontact and a high recovery strength. It was conceived that theseadvantages could be accomplished by providing contact members composedof a hard metallic matrix containing an insoluble dispersoid of adifferent metallic material having a higher vapor pressure than thematrix material when an arc was formed between the contacts and whichwould have the requisite breakdown or recovery strength.

In accordance with the foregoing, and as a specific working example,vacuum switch contact members were fabricated from an alloy composed ofabout 96 per cent nickel, 2 per cent beryllium and 2 per cent bismuth.Upon examination, these members were found to be composed ofa hardmatrix of the Ni-Be alloy containing a fine, evenly distributed bismuthdispersoidv The diamond pyramid hardness of these bodies was found to beabout 178 l(g./mm. compared to 88.1 D.P.H. for a 2 per cent berylliumcopper alloy.

When these contacts were tested and compared to silver contacts underthe same test conditions, it was found that they exhibited a recoverystrength about 50 per cent greater than the silver contacts in the rangeof 200 to 1,600 amperes and had a vacuum breakdown strength after sparkconditioning of from about 27 to 60 per cent greater than the silvercontacts (and about 25 per cent greater than copper). These contactmembers were also found to have a greater arc stability than similarcontacts made from a 20 per cent bismuth copper alloy, particularly atcurrents less than 2.5 amperes.

It will be apparent to those skilled in the art that suitable matricesother than the particular nickel beryllium alloy previously disclosedmay be employed, and dispersoids other than bismuth may be selected,depending upon the particular matrix and the operating conditions underwhich the contact members are to be used. For example, a matrix of purenickel containing a bismuth dispersoid may be used if a softer matrixmay be tolerated. It will be apparent that a matrix composed ofmolybdenum or tungsten may also be used with the dispersoid. Otherdispersoids having the requisite high vapor pressure under areconditions may also be employed. For example, an antimony dispersoid inan appropriate hard matrix may be useful. It will also be apparent thatthese kinds of contacts may have utility in electrical apparatus havinga current breaking function where the switching operation is not theprimary function of the apparatus.

What we claim is:

1. An article of manufacture comprising an electrically conductivecontact member having a contact surface consisting essentially of anelectrically conductive hard metallic matrix and a dispersoid in saidmatrix of an electrically conductive metallic material which has a highvapor pressure when exposed to the heat of an electric arc at a surfaceof said member, said dispersoid material being substantially insolublein said matrix material and substantially evenly distributedtherethrough, said matrix being primarily composed of nickel and saiddispersoid therein being bismuth, said nickel matrix material containingabout 2.0 wt. per cent of beryllium as a hardening agent.

2. An article of manufacture comprising an electrically conductivecontact member having a contact surface consisting essentially of anelectrically conductive hard metallic matrix and a dispersoid of anelectrically conductive metallic material which has a high vaporpressure when exposed to the heat of an electric are at a surface ofsaid member, said dispersaid material being substantially insoluble insaid matrix material and substantially evenly distributed therethrough,said matrix being composed primarily of nickel and said dispersoid beingbismuth, said contact member surface being composed essentially of about96 per cent by wt. nickel, 2 per cent beryllium and 2 per cent bismuth.

2. An article of manufacture comprising an electrically conductivecontact member having a contact surface consisting essentially of anelectrically conductive hard metallic matrix and a dispersoid of anelectrically conductive metallic material which has a high vaporpressure when exposed to the heat of an electric arc at a surface ofsaid member, said dispersaid material being substantially insoluble insaid matrix material and substantially evenly distributed therethrough,said matrix being composed primarily of nickel and said dispersoid beingbismuth, said contact member surface being composed essentially of about96 per cent by wt. nickel, 2 per cent beryllium and 2 per cent bismuth.